Add booleanMapper into mappers

[Siemienik]

Part of #21

TODO:

1. Create file src/mappers/booleanMapper.ts with function matches to type ValueMapper<boolean>. Which parse value string into boolean.
2. reexport it in src/mappers/index.ts
3. Prove that it works in unit test
4. Describe it in Readme.md

proposed test data provider:

const dataProvider = [
  { inValue: null, expectedResult: false },
  { inValue: '', expectedResult: false },
  { inValue: '  ', expectedResult: false },
  { inValue: '0', expectedResult: false },
  { inValue: '000', expectedResult: false },
  { inValue: 'true', expectedResult: false },
  { inValue: 'false', expectedResult: false },
  { inValue: 'a0.1', expectedResult: false},

  { inValue: '001', expectedResult: true },
  { inValue: '123', expectedResult: true },
  { inValue: '0.1', expectedResult: true},
  { inValue: '-1', expectedResult: true},
  { inValue: '   -1.2123asd', expectedResult: true}
];

tips:

• I propose to use Boolean(Number())

For making a reservation please open draft PR with this issue linked

[machadolucasvp]

Hello @Siemienik, are you sure we should expect inValue: ' -1.2123asd' be mapped to true ?

[Siemienik]

Hello @Siemienik, are you sure we should expect inValue: ' -1.2123asd' be mapped to true ?

It's quite problematic question, but when I wrote this issue I've followed the result of Boolean(Number.parseFloat()). That result true for this input.

[Siemienik]

done in #54